Hutchinson-Gilford progeria syndrome (HGPS)is a rare genetic disorder characterized by premature senescence. Affected children appear normal at birth, but within a year develop characteristic features of old age. The majority of HGPS children die from cardiac disease at an average age of 13 years. Genetic studies have identified a mutation in the lamin A/C (LMNA) gene in 18 classical HGPS cases. The mutation results in the production of a mutant lamin A protein with an internal deletion. The mechanism by which the mutated HGPS lamin A protein leads to accelerated aging is unknown. Lamin A appear to maintain nuclear structure and function through a set of specific protein interaction with other cellular factors. I therefore hypothesize that expression of the mutant HGPS lamin-A protein results in premature aging as a consequence of the . altered composition and function of lamin A-containing complexes within the nucleus. To test this hypothesis, in Aim 1 I will first define the cellular growth properties of HGPS fibroblast to identify the cellular pathways responsible for the limited life span of these cells in culture. Then in aim 2,1 will employ biochemical approaches to identify and characterize the proteins associated with wild type and mutant HGPS laminA.